The long-term objectives of research in spinal motor physiology is to determine the mechanisms by which motion is generated or coordinated by the spinal cord, and the consequences disease or injury at different points in the mechanism. The present experiments specifically investigate the role of the alpha motoneuron in locomotion, because the motoneuron is the key element in the output stages of the central nervous system. The specific aims are to determine (1) which of several synaptic summation models for the generation of the locomotor drive potential are correct and (2) whether or not allmotoneurons in a given pool are likely to be driven by the same set of interneurons. The above aims can be achieved by measuring the passive and active properties of motoneurons during locomotion. The method is to record directly from these neurons intracellularly or extracellularly with microelectrodes during voluntary locomotion in awake, walking cats. The significance of this approach can be characterized as using a complicated technique to obtain simple answers. This is a basic research project that has a wide constellation of interdigitations with targeted research efforts on paralysis, paraplegia, narcolepsy-cataplexy syndrome, epilepsy, motoneuron degenerative diseases, and muscular dystrophies. Research in this area could eventually lead to the generation of naturally coordinated locomotion in the paralyzed, injured, or diseased human spinal cord.